The first object of an artificial leg is to supply support means to reach the ground from the stump of the leg of the amputee. The proverbial peg-leg provides support at a certain point or small area on the ground, but does little to replace the feel and action of the amputee's lost foot. It often effects the rest of his body as the result of the abnormal gait it produces.
In the prior art some work has been done to provide prosthetic foot and leg which simulates the feel and action during walking of a human foot. In particular, U.S. Pat. Nos. 4,547,913, 4,822,363 and 5,217,500 to Van L. Phillips, provides a prosthetic foot and leg which, particularly in the foot portion, makes some effort to give resilience to pieces simulating the toe and the heel, respectively, of the prosthetic foot. In those structures a rigid member provides the leg portion, to which resilient add-on members simulating a toe and heel are attached, usually at about ankle level. Typically, the toe and heel pieces each extend from a common junction on a single leg piece.
Instead of a unitary structure, the present invention provides two separate cantilevered members supported from a stump socket interface, or other support, and each of which members acts essentially independently of the other, although in preferred embodiments they may even pass through one another or otherwise place limits on their normal independent action to facilitate lateral stability and in some cases to limit and/or dampen relative movements.
Since the pieces, or limbs, of the present invention are separate and individually affixed to a support, preferably to the socket interface of the stump, for cantilevered support of the member, there is also the possibility of vertical adjustment between the heel and toe pieces. Such adjustments may accommodate the prosthesis to individual comfort and feel or special desires, such as a women wishing to wear high-heeled shoes. Adjustments of both limbs may also be needed with the growth of a child amputee.
The present invention also permits adaptation of the prosthesis to provide not a substitute for a portion of a leg and foot, but rather a brace which extends along side and in planes generally parallel to the leg, although they may follow the contour of the foot. It is possible to position one limb on one side and the other limb on the opposite side of the leg. More frequently, however, pairs of limbs may be located on both sides of the leg.
In other applications, the present invention may be modified to provide a supplement to the action of a foot by incorporating it with or within a shoe.
The present invention also provides a novel mounting platform in the custom socket interface which is specifically molded to fit a particular amputee's stump. The molded socket interface can incorporate part or all of a mounting allowing attachment of the individual limbs directly to the socket interface. Depending on the receiving means for the limbs, this arrangement provides a higher point of attachment of the prosthesis as well as permitting vertical and, in some embodiments, lateral or canting adjustment of the limb.
More specifically, the present invention relates to a prosthesis simulating the feel and action during walking of a human foot and lower leg. A pair of resilient spring-like limbs, part of one of which simulates the toe, and part of the other of which simulates the heel of the foot, are supported on the leg of the wearer. Each of the limbs is composed of a resilient spring material cantilever supported by a support shank on the leg of the wearer, and each of the limbs has a curvature at least in one direction. One limb simulates a toe and front portion of the foot. The other limb simulates the heel of the foot. Both limbs, acting in concert, provide a new level of lift energy, typically at the ankle and possibly also immediately below the amputee's socket interface. In prosthetic use both the toe and front portion and the heel portion can be made broad for stability and yet be designed with flexibility to more truly simulate the action and feel of a real foot. The prosthesis of the present invention provides both terrain accommodation and a biofidelic, fluid motion response in walking simulating natural muscle flexion.